Silica is superior to other white fillers in reinforcing other rubbers, second only to carbon black. Compared silica filled vulcanizates, silica/rubber composites have the advantages of good insulation, low heat generation, high tear strength, low rolling resistance and wet skid resistance. In silica-reinforced composites, silica particles are often present in the form of loose "nebulae"-like secondary aggregates. However, SiO2 is a polar particle and has poor compatibility with a non-polar polymer, and has a strong adsorption and aggregation tendency. Therefore, the silica particles tend to be secondary agglomerated, resulting in hydrogen bond association, which is difficult to uniformly disperse in the rubber during kneading, and the desired composite effect cannot be achieved.

Therefore, it is necessary to surface-modify SiO2 to improve its compatibility with the polymer and the binding force to prepare a nanocomposite having good dispersibility and strong interfacial action. For this reason, a silane coupling agent is often added to surface-modify the silica to compensate for its insufficient performance, increase its compatibility with the rubber matrix, and weaken the filler-filler interaction.

The silane coupling agent chemically improves the interaction between the silica surface and the polymer, and weakens the filler-filler interaction. A commonly used surface-modified silane coupling agent is bis-[3-(triethoxysilyl)-propyl]tetrasulfide compound. The coupling agent reacts with the hydroxyl groups on the surface of nano-SiO2 to reduce the number of hydroxyl groups on the surface of SiO2, changing the physical and chemical properties of the surface of SiO2, changing its hydrophilicity to hydrophobicity, and improving its compatibility with rubber. Combination. The influence of silane coupling agent on the basic characteristics of vulcanization properties, mechanical properties and stress softening effects of natural rubber composites is very obvious with the particle size of silica.